Fire detector



June 21, 1955 c, w, w 2,711,457

FIRE DETECTOR Filed Feb. 9, 1953 INVENTOR. CHARLES VV. WISE A T TOHNEYS.

United States Patent 0 The present invention relates generally to firedetecting devices, and more particularly to a novel fire detectorespecially adapted for use under conditions of extreme vibration.

Modernly, there exists a need for a dependable fire detector which maybe used under conditions of extreme vibration, as for example, in thevicinity of an aircraft engine. Although such fire detectors haveheretofore been proposed, they generally prove unreliable after being inservice for a comparatively short time. Thus, such fire detectors willoften indicate a fire where none exists,

or fail to indicate the existence of an actual fire. Either type offalse indication can easily result in a disastrous situation. 7

It is a major object of the present invention to provide a novel firedetector which is completely reliable in operation.

It is another object of the present invention to provide a fire detectorof extremely simple construction utilizing but few parts, incontradistinction to the heretofore proposed devices of this naturewhich generally are very complex.

A further object of the present invention is to provide a fire detectorwhich is well adapted to withstand severe vibration over long periods oftime without requiring any attention.

Yet another object is to provide a fire detector which is light inweight whereby it is especially suited for use with aircraft.

An additional object of the invention is to provide a fire detectorwhich is readily adjustable to be responsive over a wide temperaturerange, and yet which is not adversely affected by exposure to extremeconditions of heat or cold.

It is still another object to provide a fire detector which may bemanufactured at a low cost.

lt is an additional object of the present invention to provide a firedetector which is both quick-operating and foolproof.

Other objects and advantages of the present invention will becomeapparent from the following detailed description of a preferredembodiment thereof taken in conjunction with the appended drawingswherein:

Figure 1 is a sectional view taken along the center of a fire detectorembodying the present invention;

Figure 2 is a fragmentary sectional view similar to Figure 1, butshowing parts of the fire detector in a different position;

Figure 3 is a fragmentary enlarged vertical sectional view taken onlines 3-3 of Figure l; and,

Figure 4 is an electrical wiring diagram showing an electrical circuitwhich may be utilized in conjunction with the fire detector embodyingthe present invention.

Referring to the drawings, a preferred form of fire detector embodyingthe present invention broadly comprises a heat-sensitive case member 10adapted to expand 12 nested within the case member. The case member 10includes a contact point, generally designated 14, at one of its endsand the fixed member 12 is likewise formed with a contact point,generally designated 16, disposed adjacent the contact point 14. Theopposite ends between the case member and the fixed member are rigidlyinterconnected as by spot welding 18. With this arrangement, should thefire detector be heated above a predetermined temperature, the casemember 10 will expand independently of the fixed member so as to effectengagement of the contact points 14 and 16, as indicated in Figure 2.These contact points may be included in a suitable electric circuitwhereby their engagement will set off an alarm signal. Such an electriccircuit is disclosed hereinafter.

The case member 10 will conveniently be of tubular cross section andformed of a material having a comparatively high coefiicient of linearexpansion, while the fixed member 12 may likewise be of tubular crosssection telescopically disposed within the case member. The fixedmember, however, should be formed of a material having a comparativelylow coefficient of linear expan sion. The case member and the fixedmember should preferably be heat-resistant.

One end of the case member 10 is shown rigidly secured to a plug orspool 20 as by swaging. This spool is coaxially formed with aninternally threaded bore 22. The case member and the spool should beelectrically insulated from each other. For this purpose the outersurface of the spool is shown coated with a layer of porcelain 23.Although porcelain has proven to be very well adapted for use as aninsulating medium, other insulating materials may be utilized for thispurpose. The spool bore 22 is shown threadedly engaged with a postgenerally designated 24, which post extends into the case member 10.

It will be seen that the portion of the post 24 dis posed within thecase member is of reduced diameter at that part of its length remotefrom the spool 20. One end of this reduced-in-diameter portion 26 of thepost is formed with external threads 28 adapted to receive a nut 30. Theopposite end of this reduced-in-diameter portion 26 defines a shoulder32. A washer 34 formed of an electric current conducting material isslidably disposed on the reduced-indiameter portion 26 for axialmovement therealong. This washer is shown biased against the shoulder 32by means of a helical compression spring 36 interposed between thewasher and the nut 30.

A washer 38 formed of an insulated material is carried by the post 24adjacent the outer end of the spool 20 in order to electrically insulatethe end of the case when exposed to a source of heat and a fixed membermember from the post. A metallic spacer or washer 40 is shown disposedadjacent the insulated washer 38 and an adjustment nut 42 is threadedlymounted by the post adjacent this latter washer. With this arrangement,axial adjustment of the post relative to the spool 20 may be readilyeffected. The side of the washer 34 proximate the spool 20 is seen toconstitute the contact point 14 of the case member 10. The contact point16 of the fixed member may conveniently be defined by one side of aradially inwardly extending fiange 44 integrally formed at one end ofthe fixed member.

In operation, at such time as the fire detector is heated above apredetermined temperature, the case member 10 will expand independentlyof the fixed member 12 because of the difference in their coefiicientsof linear expansion. Since these members are rigidly interconnected bythe spot weld 18 the case member must expand in a direction away fromthe post 24, or to the right in the drawings. Such movement causes theright side of the contact point 16 to be concurrently moved toward,

Patented June 21, 1955 and to finally engage, the left side of thewasher 34, as shown in Figure 2. This engagement is adapted to see oif awarning alarm signal in a manner to be set forth hereinafter.

The temperature at which the contact points 14 and 16- are to be causedto be engaged may be be readily varied by axial adjustment of the post24 relative to the spool 20. Thus, if it is desired that the firedetector provide a warning at a higher temperature, the post may berotated so as to effect its movement to the right in the drawings. If onthe other hand, the fire detector is to be set to function at a lowertemperature, the post is rotated so as to effect its movement in theopposite direction.

it should be especially noted that engagement of the washer 34 with theflange 44 cannot in any way damage the device. This is true inasmuch asupon such engagement further movement of the case member to the leftwill permit the washer 34 to be forced along the reduced-in-diameterportion 26 of the post against the yielding compressive force of thespring 36.

In order to provide a maximum rate of response for the present device,the fixed member 12 may be insulated from the case member, as by meansof a thin coating of porcelain 45 disposed upon the outer surface of thefixed member. Although porcelain is well-suited for this purpose, otherinsulating mediums may also be utilized. With this arrangement, thefixed member is prevented from absorbing as much heat as the casemember. hence any heat applied to the case member will be quicklyabsorbed and dissipated. Accordingly, the fire detector of the presentinvention may have an extremely rapid response rate.

In assembling the preferred form of fire detector disclosed herein it isanticipated that the case member, fixed member, and the spool initiallybe arranged as shown in the drawings. Thereafter, the post and contactassembly including the washer 34, spring 36 and nut 30 may be installedin the spool 20 through the right side of the device by means of theopening 49. Rotation of the post 24 relative to the spool bore 22 mayconveniently be accomplished by means of a wrench (not shown) which maybe removably inserted into the device through the opening 49. If the nut30 is rigidly secured to the post as by a pin 51, this wrench may engagethe nut 36 so as to elfect rotation of the post 24 relative to the spool20. In this manner adjustment of. the distance separating the contactwasher 34 and the flange 44 may be closely controlled. The opening 49may be sealed by means of a closure disk 50 which is adapted to besoldered or brazed in place after being pressed into the opening.

Referring now to Figure 4, the preferred form of electrical diagramutilizes a warning lamp a first lead 56 connecting the case member 19with a grounded or negative connection 53 and a second lead 60connecting the post 24 with one terminal of the lamp 54. The second leadmay be secured to the post 24 by a nut 55. Although the case member isshown grounded by lead 56, it will be apparent that it may be groundeddirectly. The opposite lamp terminal is shown connected to the positivepole 63 of a source of electric current by a third lead 64. With thisarrangement, the contact points 14 and 16 of the detector will normallybe separated, and hence no current will be permitted to flow between theground 58 and the lamp 54. At such time, however, as these contactpoints are engaged, electric current will fiow from the groundconnection 53 to the case member and then by means of the spot weldings1S and the solder or brazing used to secure the closure 50, to the fixedmember 12. From the fixed member 12 the electric current will then passthrough the post 24 by means of the washer 34 and the flange 44. Fromthe post 24 the current will pass through lead 69 to the lamp 54 so asto cause it to be illuminated. This wiring circuit permits the use oflight-in-weight components in the fire detector, as well as the use ofwire leads having a small current-carrying capacity.

Although there has been shown and described what is at present believedto be the preferred embodiment of the present invention, it will beapparent to those skilled in the art that various modifications andchanges may be made thereto without departing from the spirit of theinvention and the scope of the following claims.

I claim:

l. A fire detector, comprising: a heat-sensitive case member adapted toexpand when exposed to a source of heat; a mounting element secured toone end of said case member and electrically insulated therefrom; a postmounted by said mounting element and extending into said case member; acontact point formed on said post; a fixed member nested within saidcase member and rigidly connected thereto at a location spaced from saidmounting element; and, a second contact point formed on said fixedmember adjacent said first contact point, said case member having ahigher coefiicient of linear expansion than said fixed member wherebysaid case member is ex pandable independently of said fixed member inorder that engagement of said contact points will be eifected when saidfire detector is heated above a predetermined temperature.

2. A fire detector comprising: a heat-sensitive case member adapted toexpand when exposed to a source of heat; a mounting element secured toone end of said case member and electrically insulated therefrom, saidmounting element being formed with a threaded bore; an externallythreaded post engaged with said bore and extending into said casemember; a contact point formed on said post; a fixed member nestedwithin said case member and rigidly connected thereto at a locationspaced from said mounting element; and, a second contact point formed onsaid fixed member adjacent said first contact point, said case memberhaving a higher coefiicient of linear expansion than said fixed memberwhereby said case member is expandable independently of said fixedmember in order that engagement of said contact points will be effectedwhen said fire detector is heated above a predetermined temperature.

3. A fire detector, comprising: a heat-sensitive case member adapted toexpand when exposed to a source of heat; a mounting element secured toone end of said case member and electrically insulated therefrom, saidmounting element being formed with a threaded bore; an externallythreaded post engaged with. said bore and extending into said casemember, the portion of said post disposed within said case member beingformed with a portion of reduced cross-sectional area defining ashoulder; a washer having a contact point slidably mounted upon thereduced in cross-sectional area portion of said post; spring meanscarried by said post biasing said washer against said shoulder; a fixedmember nested within said case member and rigidly connected thereto at alocation spaced from said mounting element; and, a second contact pointformed on said fixed member adjacent said first contact point, said casemember having a higher coefiicient of linear expansion than said fixedmember whereby said case member is expandable independently of saidfixed member in order that engagement of said contact points will beelfected when said fire detector is heated above a predeterminedtemperature.

4. A fire detector, comprising: a heat-sensitive tubular case memberadapted to expand when exposed to a source of heat; a spool secured toone end of said case member and electrically insulated therefrom, saidspool being formed with a threaded here; an externally threaded postengaged with said bore and extending into said one end of said casemember; nutmeans carried by said post for effecting axial adjustmentthereof relative to said case mem her; a contact point formed on theportion of said post disposed within said case member; a tubular fixedmember telescopically disposed within said case member; means rigidlyinterconnecting the opposite end of said case member to said fixedmember; and, a second contact point formed on said fixed member adjacentsaid first contact point, said case member having a higher coefficientof linear expansion than said fixed member whereby said case member isexpandable independently of said fixed member in order that engagementof said contact points will be effected when said fire detector isheated above a predetermined temperature.

5. A fire detector, comprising: a heat-sensitive tubular case memberadapted to expand when exposed to a source of heat; a spool secured toone end of said case member and electrically insulated therefrom, saidspool being formed with a threaded bore; an externally threaded postengaged with said bore and extending into said one end of said casemember, the portion of said post disposed within said case member beingof reduced diameter for part of its length so as to define a shoulder; awasher slidably mounted upon the reduced in diameter portion of saidpost; spring means carried by said post for biasing said washer againstsaid shoulder; nut means carried by said post for effecting axialadjustment thereof relative to said case member; a tubular fixed membertelescopically disposed within said case member, said fixed memberhaving one of its ends formed with a radially inwardly extending flangedisposed adjacent said contact washer, and having its other end rigidlyfixed to the other end of said case member, said case member having ahigher coetficient of linear expansion than said fixed member wherebysaid case member is expandable independently of said fixed member inorder that engagement of said washer and said flange will be effectedwhen said fire detector is heated above a predetermined temperature.

6. A fire detector, comprising: a heat-sensitive tubuo lar case memberadapted to expand when exposed to a source of heat; a spool secured toone end of said case member and electrically insulated therefrom by aporcelain coating, said spool being coaxially formed with a threadedbore; an externally threaded post engaged with said bore and extendinginto said one end of said case member, the portion of said post disposedwithin said case member being of reduced diameter at that part of itslength remote from said spool so as to define a shoulder; anelectrically conductive washer slidably mounted upon the reduced indiameter portion of said post; a helical compression spring coaxiallydisposed upon said post for biasing said washer against said shoulder;an insulated washer carried by said post adjacent the outer end of saidspool; nut means engaged with said post adjacent said insulated washerfor effecting axial adjustment of said post relative to said casemember; a tubular fixed member telescopically disposed within said casemember, said fixed member having one of its ends formed with a radiallyinwardly extending flange disposed adjacent said electrically conductivewasher, and having its other end rigidly fixed to the other end of saidcase member, said case member having a higher coefiicient of linearexpansion than said fixed member whereby said case member is expandableindependently of said fixed member in order that engage ment of saidelectrically conductive Washer and said flange will be effected whensaid fire detector is heated above a predetermined temperature.

7. A fire detector, comprising: a heat-sensitive case member adapted toexpand when exposed to a source of heat; a mounting element secured toone end of said case member and electrically insulated therefrom, saidmounting element being formed with a threaded bore; an ex-. ternallythreaded post engaged with said bore and extending into said casemember; a contact point formed on said post; a fixed member nestedwithin said case member and rigidly connected thereto at a locationspaced from said mounting element; heat insulation means interposedbetween said case member and said fixed member; and, a second contactpoint formed on said fixed member adjacent said first contact point,said case member having a higher coefficient of linear expansion thansaid fixed member whereby said case member is expandable independentlyof said fixed member in order that engagement of said contact pointswill be effected when said fire detector is heated above a predeterminedtemperature.

8. A fire detector, comprising: a heat-sensitive tubular case memberadapted to expand when exposed to a source of heat; a spool secured toone end of said case member and electrically insulated therefrom by aporcelain coating, said spool being coaxially formed with a threadedbore; an externally threaded post engaged with said bore and extendinginto said one end of said case member, the portion of said post disposedwithin said case member being of reduced diameter at that part of itslength remote from said spool so as to define a shoulder; anelectrically conductive Washer slidably mounted upon the reduced indiameter portion of said post; a helical compression spring coaxiallydisposed upon said post for biasing said washer against said shoulder;an insulated washer carried by said post adjacent the outer end of saidspool; nut means engaged with said post adjacent said insulated washerfor effecting axial adjustment of said post relative to said casemember; a tubular fixed member telescopically disposed within said casemember, said fixed member having one of its ends formed with a radiallyinwardly extending flange disposed adjacent said electrically conductivewasher, and having its other end rigidly fixed to the other end of saidcase member, said case member also being coated with porcelain on itsouter surface, said case member having a higher coefiicient of linearexpansion than said fixed member whereby said case member is expandableindependently of said fixed member in order that engagement of saidelectrically conductive washer and said flange will be efiected whensaid fire detector is heated above a predetermined temperature.

References Cited in the file of this patent UNITED STATES PATENTS1,111,652 Fryling Sept. 22, 1914 1,935,762 Appelberg Nov. 21, 1933FOREIGN PATENTS 615,974 France Oct. 23, 1926

